Dual connectivity (DC) within a wireless mobile scenario, allows mobile user equipment to exchange user data simultaneously with more than one different base stations. For example, in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) networks, the mobile user equipment can be configured to support mobile operation of similar or different kinds. For example, mobile user equipment configured to support both LTE and Wi-Fi, or both LTE and 5G New Radio (NR), or any combination of LTE, 5G NR, Wi-Fi, or the like, may be configured by the network to utilize more than one of these links simultaneously.
Beneficially, DC can significantly improve per-user throughput and mobility robustness by allowing the mobile user equipment to be connected simultaneously to a master cell group and a secondary cell group, e.g., via a Master eNodeB (MeNB) and a secondary eNB (SeNB). The increase in per-user throughput can be achieved by aggregating radio resources from at least two eNBs. In at least some applications, coordination between participating base stations, e.g., the MeNBs and SeNBs in support of DC operation, can be achieved over existing interfaces, such as the 3GPP LTE Xn/X2 interface. More generally, DC can be achieved using different wireless access points having the same or different capabilities, such as eNBs, NodeBs, Wi-Fi, and the like.
As mobile networks evolve towards future trends, such as 3GPP 5G NR (New Radio) capabilities, it is envisioned that introduction will start with geographically limited 5G coverage, e.g., hot spots, to support high throughput using 5G, while relying on the legacy LTE network to provide an underlay coverage and reliability. In all likelihood, LTE networks will co-exist with 5G for a long time. In early stage of 5G NR deployment, 5G NR may be connected to or otherwise in communication with an LTE core system. It is conceivable that in later stages of deployment, LTE cells could be migrated to 5G Next Generation Core (NGC). In either case, UE with LTE and 5G capabilities, e.g., multiple radios, maintains single control plane (CP) connection to the mobility core network, and single or dual User Plane (UP) connection to the mobility core network.
LTE-5G NR Dual Connectivity enables new UE to connect to both LTE and 5G—achieve high throughput via 5G NR and maintain the coverage and reliability by anchoring the signaling (control plane) in LTE. DC can also minimize control plane signaling load to the core network. With the network evolving to 5G, the surrounding LTE macro cells can be of various conditions—some are suitable to be LTE anchor cell for DC, some are not.